Process heater



Aug. 30, 1966 s. A. GUERRIERI PROCESS HEATER Filed Aug. 5, 1964 g9 l'l VGA-2 F i6. [5 x20 FIG.

l O a TR NR W6 A W T m m S A %OR/VEJ United States Patent 3,269,465 PROCESS HEATER Salvatore A. Guerrieri, Rowayton, Conn, assignor to The Lurnmns Company, New York, N.Y., a corporation of Delaware Filed Aug. 3, 1964, Ser. No. 386,847 Ciaims. (Cl. 122-356) This invention relates, in general, to a new and improved process furnace and firing wall therefor, and more particularly, to a new and improved firing wall for a process furnace which provides a uniform or controllably varied radiating surface in a simple and easy manner.

In the petroleum refining industry, tube stills (using this term in its broadest sense) have been used primarily to supply sensible and latent heat to hydro-carbon streams flowing through the tubes of the furnace. For such service, the heat flux to various tubes was not especially important and hence the designs of the furnaces provided only the crudest form of control of heat flux. Even in the case of furnaces utilized in thermal cracking service, such as pyrolysis heaters for the production of ethylene, fine adjustment of heat flux was not attempted. This was true even though the cracking section of the furnace required a heat flux pattern different from he heating section, as was recognized in the prior art, wherein these two sections had been physically separated into two more or less independent heating zones.

With the advent of the use of petroleum and natural gas as the source Oif raw material for all kinds of new chemical products, relatively crude pyrolysis at moderate temperatures has been extended to extensive pyrolysis and other chemical reactions under severe conditions of temperature, pressure and residence times. For such operations, it has become imperative to achieve precise control of the heat fiux to various tubes in the furnace, and/or to various areas along the tube surfaces.

The above requirements have caused the designers to introduce gas burners of relatively small size and special design which could be distributed on the side walls of a cabin type furnace so as to approximate the required heat flux pattern. However, there are two faults with these burners. A minor fault is that they are only suitable for use with gaseous fuels. This fact is not a serious defeet, since in most instances relatively cheap fuel gases are available. Nevertheless, there are locations and services where a liquid fuel is preferred.

The other fault is the more serious one from the point of view of process requirements. Generally speaking, high performance pyrolysis furnaces must supply either a controlled constant heat flux to the tubes or a variable heat flux in accordance with the process requirements. With the multiple burner design, provision for such adjustments of heat flux requires that the operator be trained to make the necessary adjustments on a relatively large number of burners. If on the other hand, in order to keep the number of burners down to a number which can be controlled by the operator, the burners are spaced on relatively wide centers, the tube bank is, in effect, radiated from a number of point sources of radiant heat. When the burners are so spaced, those parts of the tube bank directly opposite these point sources are more intensely heated than parts which see the burner at an angle and, as a result, the heat flux to any given tube varies with position along the tube.

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Therefore, it is the general object of this invention to avoid and overcome the foregoing and other difficulties of prior art practices by the provision of a new and improved process heater and firing wall therefor.

Another object of this invention is the provision of a new and better process heater in which the heat flux variations along the process tubes within the furnace are kept to a minimum or controllably varied, as required.

Still another object of this invention is the provision of a new and better firing Wall for a process heater in which fewer burners can be utilized to achieve a uniform or controllably varied radiating surface.

A further object of this invention is the provision of a new and better firing wall for a process heater which eliminates hot spots on the tubes which are closest to the burners.

Various other objects and advantages of the invention will become clear in the course of the following description of several embodiments thereof, and the novel features will be particularly pointed out in connection with the appended claims.

For the purpose of illustrating the invention, there are shown in the drawings forms which are presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown. In the drawings:

FIGURE 1 is a cross sectional plan view of a Cabin type furnace built in accordance with the principles of the present invention.

FIGURE 2 is a sectional elevation of the furnace of FIGURE 1 taken along lines 2-2.

FIGURE 3 is a partial cross sectional plan view of one wall of a second embodiment of the present invention.

FIGURE 4 is a partial elevation of the furnace of FIG- URE 3.

FIGURE 5 is a partial cross sectional plan view of still another firing wall embodying the principles of the present invention.

In FIGURES 1 and 2 there is shown a process furnace built in accordance with the principles of the present invention and generally designated by the numeral 10. In furnace 10, the conventional straight sidewalls have been replaced with zig zag walls. The furnace 10 includes a bottom refractory wall 12 and side walls 14- and 16 supported by suitable steel columns 18. The walls 112, 14 and 16 aid in defining a heating chamber 20 within which is placed a row of horizontally positioned process tubes 22. The rows of process tubes 22 and 24- are positioned about the center line of the furnace 10. The furnace 10 is also provided with a convection unit 26 in the top thereof.

The side walls 14 and 16 are of zig-zag shape and may be mirror images of one another. Side wall 14 includes a plurality of parallel vertical sections 28, 30, 32, 3 4 and 3-6, each of which is positioned at a given angle with respect to the planes of the end walls. The sec tions 28, 30, 32, 3'4, and 36 are positioned adjacent one another. Sections 28, 30, 32, and 34 have the edge thereof furthest from process tubes 22 integral with a vertical section 4!), 4'2, 44 and 4 6, respectively. As shown, sections 40, 4 2, 44 and 46 are perpendicular to the plane of the end walls, but this is not a necessary feature. The edge of section 28 closest to the tubes 22 is integral with the end wall 38 of the furnace 1t) and the edge of section 36 furthest from the tube 22 is integral with an end wall 48. In between, angled sections 30, 32 and 34 are joined with vertical sections 40, 42, 44, 46 to form a continuous wall.

A plurality of burners 58, 60, 62, 64 and 66 are positioned in the vertical sections 40, 42, 44, 46 and the endwall 48 respectively. For example, vertical section 40 has a plurality of burners 58 spaced along the length thereof. Vertical section 42 has a plurality of burners 60 spaced along the length thereof; vertical section 44 has a plurality of burners 62 spaced along the length thereof, etc. The burners 58, 60, 62 and 64 are positioned on their respective vertical section and end wall to direct their flame generally parallel to or against the sloping wall portion immediately to the left thereof. Each burner and each row of burners 58, 60, 62, 64 and 66 has its own control valve 78, 80, 82, 84 and 86, respectively, and receives its fuel from a single fuel supply header 88. Thus, any burner or row of burners may be adjusted, or all of the burners may be adjusted at once by the valve 90 at the supply header 88.

By utilizing the zigzag shape, and directing the flame from the burners on the perpendicular vertical sections at the sloping walls immediately to the left thereof, no flame directly impinges on the process tubes 22 and 24. Rather, the flame from the burners cause the sloping walls to radiate uniformly in accordance with the intensity of the flames from the burner. Since there are a plurality of sloping wall sections along the width of the side walls 14 and 16, it is possible to controllably vary the heat flux along the width and height of the side walls and thus control the heat fluxes seen by the process tubes 22 and 24. To heat the walls evenly with a reasonable number of burners, fan-tip burners are preferred, so that the flame spreads out over the Wall surface.

In FIGURE 3, there is shown a partial horizontal cross sectional view of a second type of firing wall of a process heater built in accordance with the principles of the present invention. The firing wall 92 is intended to be utilized in place of the firing walls 14 and 16 in the furnace 10. As shown, the planes are perpendicular, but this is not a necessary feature. The wall 92 includes spaced parallel sloping angled sections 94, 96, and 98 which are joined by oppositely sloping angled sections 99, 100 and 102, disposed in planes angled to the planes of sections 94, 96 and 98. Section 94 joins the edge of section 99 closest to the process tubes with the edge of section 100 furthest from the process tubes along joining line 104. Section 96 joins the edge of section 100 closest to the process tubes with the edge of section 102 furthest from the process tubes along joining line 106.

A row of burners 108 is positioned adjacent joining line 104 in section 94. The burners 108 direct their flame parallel to or at the face of section 100. A second row of burners 110 is positioned adjacent joining line 104 on section 100 and is adapted to direct its flames parallel to or at the face of section 94. It can thus be noted that the rows of burners 108 and 110 do not have their flames directed so as to impinge on the process tubes 22 and 24 of the furnace.

Burners 103 are spaced halfway between adjacent burners 1 as illustrated in FIGURE 4. Similarly, there are positioned a row of burners 1-12 on section 96 similar to burners 108 on section 94. That is, the burners 112 direct their flame parallel to or at the face of section 102. Burners 114 are also positioned in the section 102 adjacent joining line 106 to direct their flame parallel .to or at the face of section 96. Burners 112 are staggered with respect to burners 114- in the same manner as burners 108 were staggered with respect to burners 110. The staggered relation insures uniform heating of the sections prevents interaction between the flames of one burner and another.

In FIGURE 5, there is shown a third type of firing wall 116 built in accordance with the principles of the present invention which could be substituted for the firing wall 16, or, if reversed, for the wall 14. Wall 116 includes oppositely sloped sections 118 and 120 angled to one another and oppositely sloped sections 122 and 124 angled to ane another. Adjacent, oppositely disposed sections 118 and 124 are joined by a vertical portion 126. Similarly, the section 122 is joined to an oppositely sloped section 128 by a vertical section 130. The burners for the firing wall 116 are mounted in the vertical sections 126 and 130 and are designated by the numerals 132 and 134. The burners 132, 134 are also fan-tip burners, but instead of directing their flames so as to spread over the surfaces 118, 124 etc. they direct their flames in a fan-like manner parallel to or at the oppositely sloped sections 118 and 124. In this manner, there is no direct flame on the process tubes in the furnace, but the sections will radiate heat flux in a uniform manner so as to uniformly maintain, or controllably vary, the heat flux along the length of the process tubes.

It should be noted that by utilizing angled sections, it is possible to achieve uniform heat flux for a given area of the refractory wall of the furnace without having flames impinge on the process tubes and without requiring an excessively large number of burners. It will also be easily understood that the burners 108, 1 10, 112 and 114 of firing wall 92 can be controllably varied in the same manner as were burners 58, 60, 6'2, 64 and 66 of FIGURE 1. The burners 132 and 1 34 of firing wall 116 can also be individually controlled so as to uniformly and controllably vary the heat over the length of the firing wall.

It will be understood that the embodiments of the invention set forth hereinabove are illustrative only, and that various changes in the steps, materials and arrangements of parts may be made by those skilled in the art within the scope of the invention as defined in the appended claims.

What is claimed is:

1. A process heater comprising,

a housing having a heating chamber therein;

process tubes positioned within said chamber;

said housing having a substantially vertical radiating wall within said chamber, said wall comprising a plurality of vertically extending sections, at least one of said sections being disposed at a first angle with respect to the vertical plane of said wall, and at least another of said sections being disposed at a second angle with respect to the vertical plane of said wall;

at least two vertical rows of burners mounted adjacent the edges of said sections furthest from said tubes in said chamber, said burners being positioned to direct their flames over the surface of the adjoining section; and

control means for controlling each of said vertical rows of burners.

2. The process heater as claimed in claim 1, and additionally comprising,

a common burner fuel supply means, said common burner fuel supply means supplying burner fuel to said one vertical row of burners and said second vertical row of burners through said first and second control means; and

a common control means for controlling the output of said burner fuel supply means to control all of the burners simultaneously.

3. A process heater comprising,

a housing having a heating chamber therein;

process tubes positioned within said chamber;

said housing having a substantially vertical heat radiating wall within said chamber; said wall including a first vertically extending section disposed at an angle with respect to the vertical plane of said wall;

a second vertically extending section disposed at an angle with respect to the vertical plane of said wall; and

heating means comprising a row of burners positioned near the edge furthest from said process tubes in each of said first and second sections, said burners in each section being positioned to direct flames over the surface of said other section.

4. The process heater as claimed in claim 3, wherein the burners in each of said rows are substantially equally spaced one from another, burners in one row being spaced intermediate adjacent burners of said other row.

5. In a process heater having a housing with a heating chamber therein and process tubes positioned within said chamber, said chamber having a heat radiatingwall, the improvements that comprise a plurality of vertically extending sections forming said wall, some of said vertically extending sections being at an angle to the vertical plane of said wall, and the remainder of said sections connecting the angled sections to form a continuous Wall zig zag in cross section, vertical rows of burners mounted in each said angled sections near the edge furthest from said process tubes and positioned so as to direct their flames over the surfaces'of adjoining angled sections.

References Cited by the Examiner KENNETH W. SPRAGUE, Primary Examiner. 

3. A PROCESS HEATER COMPRISING, A HOUSING HAVING A HEATING CHAMBER THEREIN; PROCESS TUBES POSITIONED WITHIN SAID CHAMBER; SAID HOUSING HAVING A SUBSTANTIALLY VERTICAL HEAT RADIATING WALL WITHIN SAID CHAMBER; SAID WALL INCLUDING A FRIST VERTICALLY EXTENDING SECTION DISPOSED AT AN ANGLE WITH RESPECT TO THE VERTICAL PLANE OF SAID WALL; A SECOND VERTICALLY EXTENDING SECTION DISPOSED AT AN ANGLE WITH RESPECT TO THE VERTICAL PLANE OF SAID WALL; AND 